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A pulsed quantum-cascade distributed-feedback laser, temperature tunable from -41 degrees C to +31.6 degrees C, and a resonant differential photoacoustic detector are used to measure trace-gas concentrations to as low as 66 parts per 10(9) by volume (ppbv) ammonia at a low laser power of 2 mW. Good agreement between the experimental spectrum and the simulated HITRAN spectrum of NH3 is found in the spectral range between 1046 and 1052 cm(-1). A detection limit of 30 ppbv ammonia at a signal-to-noise ratio of 1 was obtained with the quantum-cascade laser (QCL) photoacoustic (PA) setup. Concentration changes of approximately 50 ppbv were detectable with this compact and versatile QCL-based PA detection system. The performance of the PA detector, characterized by the product of the incident laser power and the minimum detectable absorption coefficient, was 4.7 x 10-9 W cm(-1).

-Gelled aspect in papaya fruit is typically confused with premature ripening. This research reports the characterization of this physiological disorder in the pulp of papaya fruit by measuring electrolyte leakage, Pi content, lipid peroxidation, pulp firmness, mineral contents (Ca, Mg and K -in pulp and seed tissues), and histological analysis of pulp tissue. The results showed that the gelled aspect of the papaya fruit pulp is not associated with tissue premature ripening. Data indicate a reduction of the vacuole water intake as the principal cause of the loss of cellular turgor; while the waterlogged aspect of the tissue may be due to water accumulation in the apoplast. Index terms: ultrastructural alterations, cell turgor, fruit quality, physiological disturbances, biochemical alterations. GELEIFICAÇÃO DA POLPA DE MAMÃO: AMADURECIMENTO PREMATURO OU PROBLEMAS NO ACÚMULO DE ÁGUA NO APOPLASTO?RESUMO -O aspecto geleificado da polpa de mamão é constantemente confundido com amadurecimento prematuro. Este trabalho caracterizou esse distúrbio fisiológico na polpa de frutos de mamão através de medidas de liberação de eletrólitos, conteúdo de Pi, peroxidação lipídica, firmeza da polpa, condudo mineral (Ca, Mg e K -na polpa e semente) e análises histológicas da polpa. Os resultados mostram que o aspecto geleificado da polpa de mamão não está associado com o amadurecimento prematuro. Os resultados indicam uma redução da entrada de água no vacúolo como a principal causa da perda de turgor celular, enquanto o aspecto encharcado da polpa pode ser devido ao acúmulo de água no apoplasto. Termos para indexação: alterações ultra estruturas, turgor celular, qualidade de frutos, distúrbios fisioló-gicos, alteraçõs bioquímicas.Rev. Bras. Frutic., Jaboticabal -SP, v. 32, n. 4, p. 961-969, Dezembro 2010 962

RESUMO -A emissão de etileno, a respiração e as transformações físicas e químicas em mamões da cv Golden e dos híbridos Tainung 01 e UENF/CALIMAN01 (UC01), colhidos no estádio 0 de maturação (fruto maturo com casca 100% verde) e mantidos a 25ºC° e 80% % UR foram avaliados durante a fase de amadurecimento. Os resultados mostram diferenças significativas entre os genótipos, em todas as características avaliadas. O mamão 'Golden' apresentou taxas respiratória e de emissão de etileno bastante superiores às registradas para o Tainung 01 e UC01, indicando climatério característico. O mamão UC01 foi o que manteve a coloração verde de casca por mais tempo e apresentou a menor firmeza do fruto no estádio 0. Os resultados também mostram a relação entre os picos respiratório e de etileno, com a perda de firmeza. Houve aumento no teor de sólidos solúveis (SS) no mamão UC01, não observado nos demais. A acidez titulável (AT) e a razão SS/ AT variaram durante o amadurecimento apenas na cv Golden. Os resultados indicam que os três genótipos mais comercializados no Brasil diferem fisiológica e bioquimicamente durante o amadurecimento, com os hibridos Tainung 01 e UC01 mostrando-se mais sensíveis à ação do etileno do que a cv. Golden, o que é importante ao manejo pós-colheita destes frutos. Termos para indexação:Carica papaya, emissão de etileno, genótipos de mamoeiro, respiração. RIPENING PHySIOLOGy OF VARIETIES OF PAPAyA COMMERCIALIZED IN BRAZILABSTRACT -The emission of ethylene, respiration and physical and chemical changes of papaya Golden cultivar, and of the hybrids Tainung 01 and UENF/CALIMAN01 (UC01), harvested at 0 maturity stage (mature fruit with 100 % green skin) and stored at 25°C and 80% RH have been evaluated during the ripening. The results show significant differences between genotypes in all evaluated traits. The 'Golden' papaya had shown respiratory rates and ethylene emission higher than those recorded for the Tainung 01 and UC01, indicating characteristic climacteric. The papaya UC01 has been the one which kept the green color of the skin for longer time and has shown lower firmness of fruit in 0 maturity stage. The results also show the relationship between the respiratory and ethylene peaks, with loss of firmness. There was an increase in soluble solids (SS) in papaya UC 01, not observed in the others. The titratable acidity (TA) and the ratio SS/TA did vary during ripening only in papaya 'Golden'. The results indicate that the three genotypes more commercialized in Brazil differ physiologically and biochemically during ripening, with hybrids Tainung 01 and UC01 being more sensitive to the action of ethylene than the Golden cultivar, which is important to the postharvest management of these fruits.

Polyhydroxyalkanoates (PHAs) are polymers produced from renewable resources with biodegradability and biocompatibility, being therefore attractive for medical and pharmaceutical purposes. Poly (3-hydroxybutyrate) (PHB) is the most important polymer of this family by considering the biotechnology process of its synthesis. In the present study, dense films of PHB were prepared by casting from chloroform solutions (1% m/m). Permeability studies with water, methanol, ethanol and n-propanol were performed using the gravimetric method at different temperatures (from 50 °C to 65 °C). Results provide new data on permeability coefficients of PHB membranes.

The plant hormones brassinosteroids (BR) and ethylene (ET) act together to regulate plant metabolism. We used BR and 1-methylcyclopropene (1-MCP, an ET action inhibitor) to elucidate the interactions between both hormones for the regulation of mitochondrial respiratory pathways in papaya fruit. The exogenous application of the 24-epibrassinolide (epiBR) enhanced the alternative oxidase (AOX) capacity. While treatment with Brz2001 (Brz is a specific inhibitor of the BR synthesis) also enhanced AOX capacity, these effects lacked in fruit treated simultaneously with epiBR and Brz. Changing the BR level had no effect on ET emission rate in the first 24 h, but a reduction in ET emission was observed in Brz-treated fruit on the fifth day. Together with Brz, epiBR increased the ET production on the fifth day, following the day in which the treatment was carried out. When the ET sensitivity of fruit was inhibited by the application of 1-MCP, the effects of epiBR and Brz were opposite to those obtained without 1-MCP. AOX capacity was slightly inhibited by epiBR in fruit pre-treated with 1-MCP. Data suggest that BR and ET act antagonistically, therefore regulating, directly or indirectly, AOX capacity during papaya fruit ripening.